Voltage Controlled Néel Vector Rotation in Zero Magnetic Field

Christian Binek, University of Nebraska, Lincoln

July 23, 2021

Voltage-controlled switching of remnant magnetic states paves the way towards ultra-low power and non-volatile spintronics. In this presentation, I report on a journey, which took us from isothermal electric switching of exchange bias with the help of simultaneously applied electric and magnetic fields [1] to pure voltage-controlled antiferromagnetic spintronics in zero magnetic field and at CMOS compatible temperatures [2]. Nonvolatile Néel vector reorientation in the absence of an applied magnetic field, H, is demonstrated at CMOS compatible temperatures in prototype device structures which exploit the multi-functional properties of thin films of boron (B) doped Cr2O3. Boundary magnetization associated with the Néel vector orientation serves as state variable, which is read via magnetoresistive detection in a Pt Hall bar adjacent to the B: Cr2O3 film. Switching of the Hall voltage between zero and non-zero values implies Néel vector rotation by 90-degrees. Combined magnetometry, spin resolved inverse photoemission, electric transport and scanning probe microscopy measurements reveal B-dependent TN and resistivity enhancement, spin-canting, anisotropy reduction, dynamic polarization hysteresis and gate voltage dependent orientation of boundary magnetization. The combined effect enables H=0, voltage controlled, nonvolatile Néel vector rotation at temperatures as high as 400 K. Theoretical modeling estimates switching speeds of about 100 ps making B: Cr2O3 a promising multifunctional single-phase material for energy efficient nonvolatile CMOS compatible memory applications.

[1] He, X., Wang, Y., Wu, N., Caruso, A. N., Vescovo, E., Belashchenko, K. D., Dowben, P. A. & Binek, C. Robust isothermal electric control of exchange bias at room temperature. Nat Mater 9, 579-585, doi:10.1038/Nmat2785 (2010).
[2] Mahmood, A., Echtenkamp, W., Street, M., Wang, J.-L., Cao, S., Komesu, T., Dowben, P. A., Buragohain, P., Lu, H., Gruverman, A., Parthasarathy, A., Rakheja, S. & Binek, C. Voltage controlled Néel vector rotation in zero magnetic field. Nature Communications 12, 1674, doi:10.1038/s41467-021-21872-3 (2021).

Support by ARO through MURI W911NF-16-1-0472, EPSCoR RII Track-1: Emergent Quantum Materials and Technologies (EQUATE) Award OIA-2044049, the Nebraska Nanoscale Facility: NNCI, and the Nebraska Center for Materials and Nanoscience is acknowledged.